1. Field of the Invention
The present invention relates to a power source apparatus that is suitable for a switching power source apparatus and is capable of reducing switching noise produced depending on a layout of windings or wiring.
2. Description of the Related Art
An example of a power source apparatus is disclosed in Japanese Unexamined Patent Application Publication No. 2001-53459 (in particular, FIG. 2 thereof). This power source apparatus is a thin-type power source apparatus having a metal base, a radiator attached to the metal base, circuit parts arranged on the metal base, a case covering the circuit parts and attached to the metal base, and a stud to attach the metal base including the radiator and case to a board. A winding is connected to an insulated copper foil pattern of the metal base.
FIG. 1 illustrates a power source apparatus of this type according to a related art. In FIG. 1, an AC power source AC provides a sinusoidal voltage, a bridge rectifier DB rectifies the sinusoidal voltage into a pulsating voltage, and a step-up-type power factor corrector steps up the pulsating voltage and corrects the power factor thereof. The step-up-type power factor corrector includes a reactor L1, a diode D1, a switching element Q1, and an output smoothing capacitor Co. An input capacitor Ci is to absorb normal-mode switching noise.
Operation of the power source apparatus illustrated in FIG. 1 will be explained. The sinusoidal voltage from the AC power source AC is rectified by the bridge rectifier DB, and through the input capacitor Ci, a full-wave-rectified waveform is supplied to the power factor corrector. A first controller 10 conducts ON/OFF control of the switching element Q1.
When the switching element Q1 is turned on, a current passes through a path extending along AC, DB, Ci, L1, Q1, Ci, DB, and AC, to accumulate energy in the reactor L1. When the switching element Q1 is turned off, the energy accumulated in the reactor L1 is combined with the voltage from the AC power source AC, to charge the output smoothing capacitor Co through the diode D1.
The stepped-up voltage supplied to the output smoothing capacitor Co is higher than a peak value of the sinusoidal voltage. Namely, the first controller 10 controls an input current and an output voltage, so that the voltage of the output smoothing capacitor Co keeps a constant value and the input current has a sinusoidal waveform similar to the input voltage.